Abstract: Based on the test and simulation analysis of aluminum shell defect specimens, three methods of phased array inspection (PA), conventional ray test (RT) and conventional ultrasonic testing (UT) for welding seam detection of aluminum shell of the gas-insulated transmission lines were studied and compared. The test results show that the detection rate of UT and PA is superior to that of RT for face-type defects with greater hazards.Phased array detection (PA) is easier to detect the best angle of defects, has a higher detection rate for hazardous defects. Moreover, PA can obtain more information of defect feature. The test results provide a basis for the non-destructive testing process of gas insulated transmission line (GIL) shell in Sutong pipeline corridor project.